KR20170055082A - Electron emitting material and process for preparing the same - Google Patents
Electron emitting material and process for preparing the same Download PDFInfo
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- KR20170055082A KR20170055082A KR1020150157671A KR20150157671A KR20170055082A KR 20170055082 A KR20170055082 A KR 20170055082A KR 1020150157671 A KR1020150157671 A KR 1020150157671A KR 20150157671 A KR20150157671 A KR 20150157671A KR 20170055082 A KR20170055082 A KR 20170055082A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/02—Details
- H01J61/04—Electrodes; Screens; Shields
- H01J61/06—Main electrodes
- H01J61/067—Main electrodes for low-pressure discharge lamps
- H01J61/0675—Main electrodes for low-pressure discharge lamps characterised by the material of the electrode
- H01J61/0677—Main electrodes for low-pressure discharge lamps characterised by the material of the electrode characterised by the electron emissive material
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G27/00—Compounds of hafnium
- C01G27/06—Sulfates
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B33/00—Electroluminescent light sources
- H05B33/12—Light sources with substantially two-dimensional radiating surfaces
- H05B33/14—Light sources with substantially two-dimensional radiating surfaces characterised by the chemical or physical composition or the arrangement of the electroluminescent material, or by the simultaneous addition of the electroluminescent material in or onto the light source
Abstract
Description
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron emitting material and a method of manufacturing the same, and more particularly, to an electron emitting material capable of increasing a discharge current at a low driving voltage with a low work function and a method of manufacturing the same.
Field Emission Display (FED) is a device that emits electrons and displays images by emitting phosphors. It is one of the core technologies of large-area displays because of its advantage of thinness. In addition, since a fluorescent tube or an illumination device uses a micro electron source having an electron emitter that emits electrons by a strong current, by using a material having excellent electron emission characteristics and reducing the diameter of the tube, So that it can be applied to a backlight of a non-light emitting type display device such as a liquid crystal display.
The prior art used in a FED or a fluorescent tube uses a principle in which an electron beam is emitted from an electron emitter by applying a high voltage between an electron emitter and an electrode material and excited by a phosphor to emit light. As the electron emission material, a metal such as Mo or a carbon-based material is mainly used.
In order to facilitate the driving of the minute electron source, it is required to drive at a low voltage. Especially when the electron emission is controlled by on / off of the driving voltage like the FED, it is necessary to lower the driving voltage. Therefore, it is necessary to develop a material having a small work function capable of increasing the emission current from the electron emitter at a low driving voltage. Currently used metal or carbon-based materials such as Mo have a work function which is directly related to easiness of electron emission, which is as large as 4 eV, so that a method of inducing concentration by forming a fine needle-shaped structure for electron emission at a low voltage is used. For example, in the case of Mo, it needs to be processed into a cone shape with a height of 1 μm. In the case of carbon, it is necessary to use a structure having a diameter of several tens of nanometers, such as carbon nanotubes. However, the electron emitter structure of this shape is difficult to process the electrode, and if the interval between the electrodes is narrowed, there arises a problem in device fabrication and driving reliability.
It is an object of the present invention to provide an electron emissive material having a very large electron emission effect by exhibiting low work function properties from the presence of a localized electron layer.
It is also an object of the present invention to provide a method for producing the electron emission material.
The present invention provides an electron emission material represented by the following formula (1).
≪ Formula 1 >
Hf 2 + x S (0? X? 0.4)
The electron emission material may further include a Hf-O compound layer on the surface. At this time, the Hf-O compound layer is preferably included in the range of 0.001 to 10%. If it is smaller than the lower limit of the above range, the stability can not be maintained, and when the upper limit is exceeded, the efficiency of electron emission is reduced.
The electron emission material may further include a layer of Hf-S-O compound on the surface thereof. At this time, the Hf-S-O compound layer is preferably included in the range of 0.001 to 10%. If it is smaller than the lower limit of the above range, the stability can not be maintained, and when the upper limit is exceeded, the efficiency of electron emission is reduced.
The present invention also provides an electronic emitter characterized in that the composite-type electron emission material powder is exposed on the surface.
The present invention also provides a fluorescent tube comprising the electron emitter.
The present invention also provides a method for producing a compound, comprising: a first step of mixing a Hf powder and an S powder, followed by heat treatment at a temperature of 500 to 600 ° C for 3 to 4 days to obtain a compound raw material; And a second step of melting and cooling the compound raw material obtained in the first step.
It is preferable that the melting proceeds in an inert gas atmosphere.
The second step is preferably repeated one or more times.
The manufacturing method may further include a step of pulverizing the produced composite electron emission material by ball milling, induction milling, high energy milling, jet milling, or grinding using a mortar.
The manufacturing method may further include the step of pulverizing the produced composite electron emission material by gas atomization.
In the first step, the Hf powder is preferably added in a ratio of 2 to 2.4 mol based on 1 mol of the S powder.
The electron emission material of the present invention exhibits a very large electron emission effect due to the manifestation of low work function characteristics from the presence of the localized electron layer of the Hf 2 + x S material.
The work function of Hf 2 + x S provided in the present invention does not depend much on x and shows a value of about 2.7 eV. This is 30% lower than the work function of 4 eV of commercial electron emission materials Mo and carbon. When applied to FED and fluorescent tube, large emission current can be obtained at low driving voltage without changing the existing device structure .
By using the method for producing Hf 2 + x S electron emitting materials provided in the present invention, mass production of materials can be achieved by simple heat treatment, melt-solidification and mechanical grinding processes.
The electron emission material provided in the present invention is, for example, easy to manufacture and can emit electrons with a low driving voltage. Thus, it enables the implementation of an electronic emitter that forms a relatively large emission current on the same applied voltage basis, which can be applied to low voltage driven FEDs, fluorescent tubes and lighting devices.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a crystal structure diagram of Hf 2 S which is a matrix of an electron emission material of the present invention. FIG. There is a localized electron layer between layers and is a source of low work function properties.
Figure 2 is a Hf 2 .4 S, Hf 2 .2 X- ray of the S and Hf 2 S is diffraction analysis results produced in Example 1.
Figure 3 is a Hf 2 .4 S and the electrical resistance and charge density measurement results for the Hf 2 S produced in Example 1. Fig.
Figure 4 is a TEM photograph of the microstructure of the Hf 2 .4 S and Hf S 2 powder prepared in Example 1. Fig.
Figure 5 is one embodiment of Hf 2 .4 embodiment a 120 hour exposure to 120 hours, or S powder in water in the air, for example, a two X- ray diffraction analysis results of the experiment in the manufacturing.
Figure 6 is an embodiment 1 and Hf 2 .4 S, a work function of the measurement result of the Hf 2 S, Mo and C prepared in Comparative Example 1.
BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and how to accomplish them, will become apparent by reference to the embodiments described in detail below with reference to the accompanying drawings.
However, the present invention is not limited to the embodiments described below, but may be embodied in various forms.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. Only.
Thus, in some embodiments, well-known components, well known operations, and well-known techniques may be omitted in order to avoid obscuring the present invention.
In this specification, the singular forms include plural forms unless the context clearly dictates otherwise, and the constituents and acts referred to as " comprising (or having) " do not exclude the presence or addition of one or more other constituents and actions .
Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs.
Hereinafter, the electron emission material according to the present invention and a method for producing the same will be described in detail.
According to one embodiment of the present invention, there is provided an electron emission material comprising Hf and S and having a composition represented by the following formula (1).
≪ Formula 1 >
Hf 2 + x S (0? X? 0.4)
The electron emission material includes localized interlayer electrons of high density and exhibits a large electron emission effect due to its low work function. The electron concentration can be increased by adjusting the ratio of Hf.
In one embodiment, the Hf 2 + x S powder of formula (1) may be a complex-shaped material forming a film several tens of nanometers thick comprising a compound consisting of Hf and O or Hf, S and O on the surface.
The Hf-O compound layer is preferably included in the range of 0.001 to 10%. If it is smaller than the lower limit of the above range, the stability can not be maintained, and when the upper limit is exceeded, the efficiency of electron emission is reduced.
The Hf-S-O compound layer is preferably contained in the range of 0.001 to 10%. If it is smaller than the lower limit of the above range, the stability can not be maintained, and when the upper limit is exceeded, the efficiency of electron emission is reduced.
The electron emission material may be in powder or bulk form. The bulk electron emission material may be a single crystal or a sinter produced by sintering.
According to an embodiment of the present invention, there is provided a method for producing a compound, comprising: mixing a Hf powder and an S powder; and heat treating the mixture at a temperature of 500 to 600 ° C for 3 to 4 days to obtain a compound raw material; And a second step of melting and cooling the compound raw material obtained in the first step.
The first step is a step of heat-treating the mixture of raw materials for preparing an electron emission material for seed phase synthesis before the melting process.
Specifically, Hf and S raw materials vacuum-sealed in a silica tube are placed in a furnace and heat-treated at 500 ° C for 10 hours.
The second step is to increase the purity and homogeneity of the electron emission material.
Specifically, the heat-treated mixture prepared in the first step is placed in an arc melting furnace chamber, and an inert gas atmosphere such as Ar is formed at a level capable of arc driving after forming a vacuum atmosphere. Then arc is applied to melt the heat-treated mixture and solidify to produce an electron-emitting material.
The third step is a step of producing a powder.
Specifically, a powder is prepared by using a mechanical milling process such as ball milling of the massive material produced in the third step.
The melting process may be performed by a process selected from the group consisting of a commonly used melting process, for example, a high temperature tubular furnace, an ultra-high temperature furnace, and the like. Preferably, the melting process may be performed by arc melting. But is not limited to, and can be used as a melting method in the art. By using the arc melting method, industrial mass production of electron emission materials is possible. Even when a general melting method other than the arc melting method is used, improved physical properties can be obtained.
In the arc melting method, the raw material is melted in an inert gas atmosphere for preventing oxidation of the mixed raw material by heating the raw material to a melting point or higher to form a liquid state. It is possible to obtain the electron emission material of the size and shape corresponding to the sample loading part made of the copper material in the arc melting facility chamber. Melting by arc melting can be repeated to increase the purity and homogeneity of the electron emission material.
The molten-solidified material may be pulverized by ball milling, attrition milling, high energy milling, zet milling, grinding in a mortar, or the like. However, the present invention is not limited thereto, and any method that can be used in the related art can be used as a method for producing powders by pulverizing raw materials by dry or wet methods.
Alternatively, the electron emission material powder may be prepared by gas atomization. In the gas atomization method, the raw material of the compound prepared by the melting method is heated to a melting point or higher to form a liquid state, and rapidly injected into a vacuum or argon atmosphere at room temperature through a nozzle to quench the raw material powder.
Alternatively, the raw material powder may be prepared by a plasma process. The gas atomization method can obtain spherical raw material powders by vaporizing the raw material of the compound prepared by the melting method and quenching the raw material powder. However, it is not necessarily limited to these, and a method of producing powders by the rapid solidification process may be used Anything that can be done is possible.
≪ Example 1 > Hf 2 + x S (x = 0, 0.2, 0.4) Manufacturing and Characterization
Crushed Hf and S powder are pelletized and vacuum-packed in a silica tube, and then put into a furnace and sintered at 500 ° C for 70 hours. Since Hf 2 + x S is a phase at high temperature, S is a very low vaporization point, so pure S is made into a compound of Hf-S through the above sintering process to minimize the loss of S during material melting for synthesis. The intermediate material made by sintering is synthesized by arc melting method and then pulverized by ball milling or the like.
As shown in the XRD pattern shown in [Fig. 2], the prepared raw material forms a single phase which is the same as the Hf 2 S crystal structure in the range of 0 ≦ x ≦ 0.4 of the Hf 2 + x S composition.
After forming the synthesized Hf 2 + x S into a plate-like rectangular parallelepiped shape, Au electrodes are deposited for measuring the resistance and for measuring the Hall terminal. Place the electrode-formed sample in the instrument and measure the change in resistance and Hall coefficient with temperature.
As a result of the resistivity measurement according to temperature, the produced material is a typical metallic material having a low resistivity at a low temperature. As a result of the measurement of the charge density through the Hall coefficient measurement, it has a high charge density of ~ 10 22 cm 3 . This material has a small change in resistivity and charge density in the range of 0 ≤ x ≤ 0.4 of Hf 2 + x S composition.
The work function of the raw material was measured by XPS. In order to remove the oxide film which may exist on the surface, the raw material was placed in the XPS and the surface was removed by plasma for 40 hours, and the measurement was performed.
As shown in Fig. 5, the work function of Hf 2 S was 2.7 eV, and the work function of Hf 2 .4 S was 2.67 eV, which was a low value that can be compared with the work function of alkali metal, and 0 ≦ x ≦ 0.4 There was little change in work function in the range.
≪ Comparative Example 1 > Measurement of Mo and C work function
The work function was measured in the same manner as in Example 1 for Mo and C, respectively.
As shown in FIG. 5, Mo and carbon-based materials commonly used as electron emission materials have a work function of 4 eV or more. However, in the case of the Hf 2 + x S raw material synthesized by the present inventors, a material having a work function of about 2.6 eV regardless of the composition of x in a range of 0 ≦ x ≦ 0.4 is used as a material having a work function of a metal such as Mo or a carbon- Since it has a remarkably low work function, electron emission is relatively easy at a low voltage.
≪ Example 2 > Hf 2 + x S stability evaluation
To evaluate the stability of Hf2 + xS, the raw powders were oxidized in air or in water for 120 hours. As shown in the XRD pattern of [Fig. 5], no oxide peak appeared after 120 hours in all the raw materials which were oxidized in water.
Further, the state of the raw material surface was confirmed through TEM imaging and EDS measurement. As shown in FIG. 4, an amorphous layer formed of Hf and O on the surface of the raw material was formed to a thickness of several to several tens of nanometers to suppress further oxidation of the raw material.
The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.
Claims (13)
≪ Formula 1 >
Hf 2 + x S (0? X? 0.4)
And a Hf-O compound layer on the surface.
Wherein the Hf-O compound layer is contained in the range of 0.001 to 10%.
And a Hf-SO compound layer on the surface of the Hf 2 + x S powder.
Wherein the Hf-SO compound layer is contained in the range of 0.001 to 10%.
And a second step of melting and cooling the compound raw material obtained in the first step.
Wherein the melting is performed in an inert gas atmosphere.
Wherein the second step is repeated one or more times.
Characterized by further comprising the step of pulverizing the produced composite electron emission material by a ball milling, an induction milling, a high energy milling, a jet milling or a crushing method using a pestle bowl .
Characterized by further comprising the step of pulverizing the produced composite-type electron emission material by gas atomization.
Wherein the Hf powder is added in a ratio of 2 to 2.4 mol based on 1 mol of the S powder in the first step.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101965813B1 (en) * | 2017-11-15 | 2019-04-05 | 성균관대학교 산학협력단 | Stable amorphous electron emission materials in air and manufacturing method thereof |
| KR20190055697A (en) * | 2017-11-15 | 2019-05-23 | 성균관대학교산학협력단 | Low work function electron emitters and manufacturing method thereof |
| WO2019146912A1 (en) * | 2017-11-15 | 2019-08-01 | 성균관대학교산학협력단 | Electride thin film and organic/inorganic light emitting device comprising same |
| WO2019146913A1 (en) * | 2017-11-15 | 2019-08-01 | 성균관대학교산학협력단 | Catalyst for hydrogen evolution reaction, comprising copper promoter |
| KR20220109795A (en) | 2021-01-29 | 2022-08-05 | 김여정 | Desktop Smart Mirror |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101884691B1 (en) * | 2017-03-09 | 2018-08-30 | 성균관대학교 산학협력단 | Catalyst for hydrogen evolution reaction |
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2015
- 2015-11-10 KR KR1020150157671A patent/KR101757309B1/en active IP Right Grant
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101965813B1 (en) * | 2017-11-15 | 2019-04-05 | 성균관대학교 산학협력단 | Stable amorphous electron emission materials in air and manufacturing method thereof |
| KR20190055697A (en) * | 2017-11-15 | 2019-05-23 | 성균관대학교산학협력단 | Low work function electron emitters and manufacturing method thereof |
| WO2019146912A1 (en) * | 2017-11-15 | 2019-08-01 | 성균관대학교산학협력단 | Electride thin film and organic/inorganic light emitting device comprising same |
| WO2019146913A1 (en) * | 2017-11-15 | 2019-08-01 | 성균관대학교산학협력단 | Catalyst for hydrogen evolution reaction, comprising copper promoter |
| WO2019156337A1 (en) * | 2017-11-15 | 2019-08-15 | 성균관대학교산학협력단 | Amorphous electron emitting material stable in air and manufacturing method therefor |
| KR20220109795A (en) | 2021-01-29 | 2022-08-05 | 김여정 | Desktop Smart Mirror |
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